Pump device



Oct. 25, 1955 C. G. TERMONT PUMP DEVICE Filed Feb. 9, 1953 FIG. 2

INVENTOR. C.G- TERMONT ATTORNEYS United States Patent PUMP DEVICE Charles G. Terrnont, Moline, Iil., assignor to Deere & Company, Moline, Ill., a corporation of Illinois Application February 9, 1953, Serial No. 335,924

4 Claims. (Cl. 103 -271) This invention relates to a two-speed hydraulic system and more particularly to a fluid-pressure system capable of selectively delivering maximum volume at lower pressures and maximum pressures at reduced volumes.

A system of the general character referred to is particularly useful in moving loads or performing other work wherein the load is apt to vary in magnitude during a certain range of operation. In one particular example, such a situation exists in the use of a tractor-mounted material loader of the type comprising a subframe carried on the tractor and itself mounting. a pair of forwardly extending booms or arms to the free ends of which is carried aload-carrying bucket. Fluid motors in the form of hydraulic cylinders are ordinarily used to elevate the booms after the bucket has accumulated a load. It is found in many cases than the initial efiort required to lift the loaded bucket is materially greater than that 1 required to raise the arms and bucket after the initial stage has been passed. This is particularly true when handling material that may be compacted or material that may have an initial adherence to the ground, such as frozen material of a relatively fluent nature. In cases of this type, a one-speed hydraulic system designed to deliver maximum power will be found adequate under extreme conditions but will be found to be too slow in the majority of circumstances. Therefore, it isexpedient to provide a system capable of operation at variable speed.

The present invention has for a principal object the provision of such system, It is an important object of the invention to achieve a system whereby the speeds may be obtained simply and economically by the provision of a relatively uncomplicated device for volumetrically augmenting the-output-of a fluid pump, even though at the expense of pressure. Incorporated in this object is the provision of means for cutting out the Volumetric increase so that maximum pressure may be delivered.

A further object of the invention in this respect is to make 1 the selection between lower and higher pressures automatic.

In a preferred embodiment of the invention, the means for accomplishing the foregoing and other objects comprises a housing or other medium appropriately establishing a chamber into which fluid is supplied via a jet or nozzle from a fluid pump. The arrangement of the jet relative to the inlet of the chamber and relative to the inlet of a secondary line from a secondary source of supplysuch as a fluid reservoiris such that the delivery of the pump through the jet causes fluid to flow through the secondary line into the chamber to augment the vol ume delivered by the pump. The outlet end of the chamber is connected to the fluid motor or equivalent device. A by-pass line is connected between the discharge side of the pump and the inlet side of the motor and has less restriction than the jet so that the jet and secondary source may be bypassed under certain conditions. The by-pass line is normally closed by a biased valve which is openable in response to the increase in working pres- "ice sure in the system in excess of a predetermined maximum, so that when working pressures are below the predetermined maximum, fluid delivery from the pump is through the jet and augmented by the secondary source of supply so that the motor or equivalent device is operated at its highest. speed for which the system is designed. But, when working pressures exceed the predetermined maxi mum, the by-pass is opened and the pump delivers its maximum output although at reduced volume so that the motor or other hydraulic device will deliver more power but at a slower speed.

The foregoing and other important objects and desirable features inherent in and encompassed by the invention will become apparent as a disclosure of a preferred embodiment of the invention is made in the following detailed description and accompanying sheet of drawings.

In the drawings,

Figure 1 is a perspective view of a representative type of tractor-mounted loader in which the system may be used.

Figure 2 is a schematic view of the fluid system, including a portion thereof in section showing oneform-of means for obtaining variable speed operation.

The material loader chosenfor purposes of illustration in Figure 1 comprises a tractor 10 equipped with a rigid subframe 12 to which are pivoted the rear ends of :a pair of booms or arms 14, the pivot for the left-hand arm being shown at 16. The forward or free ends of the arms or booms carry therebetween a material-handling bucket 18; and the rear end portions of the subframe include rigidly upstanding arms 20, between the upper ends of which and .midportions of the booms 14 are connected fluid motors such as hydraulic cylinder and piston assemblies 22. Although the nature of the drawing in Figure 1 shows only one arm and one motor 22, it will be understood that the construction is repeated at the right-hand side of the machine. The numeral 24 designates a main control valve which may be manually operated by the tractor operator by means of a control valve lever 26. The construction so far described may be replaced by any conventional design, that illustrated being shown as an example of the hydraulic system.

In the schematic and sectional illustration embodied in Figure 2, one of the hydraulic motors or piston and cylinder assemblies 22 is illustrated as including a movable piston 28 and as having an inlet 30 and an outlet 32 (although the inlet and outlet become interchanged selectively during operation of the motor).

The tractor may be conventionally equipped with a self-contained system to the extent that it will include a reservoir 34 and a fluid pump 36. The pump maybe conventionally driven from any suitable part of the tractor, such as the engine cam shaft or the conventional power take-cit, all of which is relatively immaterial here. The reservoir 34 is vented to the atmosphere and to that extent is pressurized, since it is subject to atmospheric pressure. The main control valve 24 is interposed between the motor 22 and the reservoir 34 and pump 36 and has an exhaust line 38 leading to the reservoir and a high-pressure line 40 connected to the pump 36 by means that will be presently described.

The pump 36 has an inlet 42 conventionally communicating with the reservoir 34 and further has an outlet or discharge line designated generally by the numeral 44.

The means for causing the motor to operate at variable speeds comprises essentially a housing 46 having a fluid outlet 48 connected to the high-pressure line 40. The interior of the housing 46 is formed as a chamber 50 having near its outlet end an enlarged portion or dome 52 and having a pair of inlets 54 and 56. The inlet 56 is connected by a secondary or suction line 58 to the reservoir 34 and this line includes a check valve 60 for preventing reverse flow of fluid in the suction line. The discharge outlet 44 of the pump 36 leads into the inlet of the housing 46 by what may be said to be first and second branches 62 and 64.

The first branch is in the form of a restricted nozzle or jet and discharges into the chamber 50 via a reduced or Venturi portion 66. The lower part of the Venturi is enlarged and embraces the jet 62, as shown at 63. It is into this latter portion that the secondary or suction line 58 leads via the inlet 56. The arrangement is such that fluid delivery through the jet 62 into the chamber 50 through the Venturi 66 creates in the portion 68 a subatmospheric pressure zone, whereby fluid from the secondary source comprising the reservoir 34 is caused to pass the check valve 60 andflow through the line 58 into the chamber 50 to augment volumetrically the supply of fluid from the pump 36 via the jet 62.

The second branch 64 comprises part of a bypass line 70 having its other end in communication with the motor inlet, here via the chamber outlet 48 and high-pressure line 40 between the outlet 48 and the valve 24. Accordingly, the jet action may be cut out and fluid delivered through the by-pass 70 directly through the high-pressure line 40 to the motor 22 (it being assumed that the main control valve 24 is open so as to pass fluid to the motor).

The by-pass line is under the control of an automatic by-pass valve, designated generally by the numeral 72. For the purpose of carrying the bypass valve 72 in the bypass line 70, the housing 46 includes an integral portion in the form of a thimble or sleeve 74 coaxial with a bore 76 in a wall 78 that separates the chamber 50 from the by-pass 70. The by-pass valve '72 is of the spool type and is axially slidable in the bores at 7476, being normally biased to a closed position blocking the by-pass line 70 by means of biasing means comprising a spring 80. The spring 80 is calibrated to close the by-pass valve 72 against a stop 82 in the wall 78 when working pressures in the system are below a predetermined maximum Accordingly, pump delivery is directed through the jet 62 and chamber 50 to be augmented by the supply of secondary fluid via the suction line 58, which means that the motor 22 may be operated at a higher speed, although it will deliver less force. The left-hand end of the bypass valve 72 constitutes a pressure-receivable area $4 exposed to working pressures in the system and the valve is arranged to move under certain pressure to an open position enabling the pump to discharge via the by-pass line 70 to the motor 22 (via the valve 24, of course). Consequently, when working pressures exceed the predetermined maximum, the by-pass valve 72 shifts to the right against the bias of the spring 80 and opens the by-pass line 7%. Since the restriction in the by-pass line is considerably less than that set up at the jet 62, fluid will flow at a lower rate but at a higher pressure through the by-pass line and high-pressure line 40, which means that the motor 22 will deliver more force but will operate at a lower speed. When the load becomes such that the working pressure drops below the predetermined maximum, the biasing spring will re-close the bypass valve 72 and high-speed operation via the jet 62 will again be attainable.

The sleeve or thimble 74 which carries the valve 72 and which also encloses the biasing spring 89 is closed by a vented plug 86 for obvious purposes.

The sizes and proportions of the chamber, the jet, the Venturi and the by-pass may all be changed to accommodate the requirements of a particular situation. Those proportions etc. shown are merely representative.

Various other modifications of the invention will undoubtedly occur to those versed in the art, all of which may be achieved without departing from the spirit and scope of the invention.

What is claimed is:

l. A dual pressure control device, comprising: means including a chamber having a pump inlet leading into the chamber, a motor outlet leading out of the chamber and a reservoir inlet leading into the chamber intermediate the pump inlet and the motor outlet; jet means communicating with the pump inlet and leading into the chamber in such position relative to the reservoir inlet that fluid flow through the jet and into the chamber from the pump inlet draws additional fluid through the reservoir inlet for augmenting the volumetric discharge through the motor outlet; a by-pass line leading from the pump inlet to the motor outlet and by-passing the jet; and a valve in the by-pass line movable between first and second positions respectively to open and close the by-pass line, said valve having a fluid-pressure-receivable area subject to fluid pressure at the motor outlet, said valve being biased to its closed position and being movable to its open position in response to a predetermined pressure at the motor outlet.

2. The invention defined in claim 1, in which: the chamber, the by-pass line and the jet are integral in a housing and the pump and reservoir inlets and the motor outlet are openings through the housing and communicating with the chamber.

3. The invention defined in claim 1, in which: the chamber has a restricted throat into which the jet discharges and an enlarged dome beyond the throat; the motor outlet exits from the dome; and the reservoir inlet enters the chamber ahead of the throat.

4. The inventiondefined in claim 3, in which: the communication of the by-pass line with the motor outlet is via the dome.

References Cited in the file of this patent UNITED STATES PATENTS 1,417,853 Nash May 30, 1922 2,203,077 Carpenter June 4, 1940 2,525,256 Byram Oct. 10, 1950 2,527,458 Schurr Oct. 24, 1950 FOREIGN PATENTS 896,302 Germany Nov. 12, 1953 

